Solution: A river lies in the east - west direction. The current in the river has a velocity relative to the ground of 3 mi/hr toward the east. A boat has a maximum speed relative to the water of 4 mi/hr. The b

Problem

A river lies in the east - west direction. The current in the river has a velocity relative to the ground of 3 mi/hr toward the east. A boat has a maximum speed relative to the water of 4 mi/hr. The boat is heading so as to get across the river as soon as possible. If the river is one mile wide, how long does it take the boat to cross the river?